JP3852623B2 - Method for producing ferrite sintered body - Google Patents
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Description
【０００１】
【産業上の利用分野】
本発明は、従来技術による製品と同等以上の特性を持つＭｎ―Ｚｎ系ソフトフェライトを、安価に製造するためのソフトフェライト原料粉に関し、特に高透磁率特性を有するＭｎ―Ｚｎ系ソフトフェライト原料粉、フェライト焼結体及びその製造方法に関するものである。
【０００２】
【従来の技術】
従来のＭｎ―Ｚｎ系ソフトフェライトは、Ｆｅ2Ｏ3、Ｍｎ3Ｏ4、ＺｎＯの各酸化物を所定量に秤量し、混合し、その混合体を８００〜１０００℃で仮焼し、仮焼された仮焼体を粉砕し、所望の添加物及びバインダーを添加し、造粒し、それを金型内に充填し、所定の形状に成形し、１３００〜１４００℃の高温で焼成して、研磨工程等の必要な加工を経て、Ｍｎ―Ｚｎ系ソフトフェライトコアが得られている。
このように、従来のＭｎ―Ｚｎ系ソフトフェライトを得る方法は、工程が長く、煩雑で、仮焼及び本焼成と２回の焼成工程を経る為、コストが嵩むという問題があった。
この仮焼を行う理由は、成分の均質化、フェライト化反応の促進等であり（平賀・奥谷・尾島著、フェライト、丸善、昭６１．１１．３０、ｐ４８〜５１）、もし仮焼をしていない生の原料粉を直接造粒、成形、焼成すると、５００〜９００℃でのフェライト化反応による体積膨張、及びそれに引き続く焼結反応による体積収縮により、変形やひび割れが起こるという問題が生じる。
【０００３】
一方で、仮焼工程省略及び品質向上を狙った改良技術として、Ｆｅ、Ｍｎ等を含む複合酸化鉄粉を得る方法もいくつか提案されている。
例えば、特公昭４７―１１５５０号、特公昭６３―１７７７６号のように、フェライト構成金属の塩化物を水溶液状態で混合した後、高温ガス中で噴霧・焙焼し、直接仮焼粉相当の粉体を得る方法がある。この方法は、仮焼工程省略によるコストダウンの他に、溶融状態での混合の為、従来より成分の均質化に優れ、品質が向上するというメリットも期待されている。
【０００４】
また、このＭｎ―Ｚｎ系ソフトフェライト原料粉の主要な用途の一つに、通信機器等のトランスおよびノイズフィルタ等がある。このような通信機器に使用されるＭｎ―Ｚｎ系ソフトフェライトは、製品の軽量化、薄型化および小型化のために、高透磁率であることが望まれている。この高透磁率を得るには、結晶粒径が大きく、かつ均一であることが良いとされ、焼成工程では、高温で長時間焼成が行われている。
【０００５】
【発明が解決しようとする課題】
従来の複合酸化鉄粉を得る方法では、特公昭６３―１７７７６号にも記述されている様に、塩化物の蒸気圧が高いＺｎが先に揮散してしまい焙焼後の複合酸化鉄粉体に取り込まれ難い、という問題がある。
この問題を解決する為に、特公昭６３―１７７７６号では、ＺｎＯはフェライト化反応を起こし易いという特長を利用して、塩化物蒸気圧の低いＦｅとＭｎの塩化物水溶液のみを混合・噴霧焙焼し、得られた粉体に後からＺｎＯ粉末を混合して造粒・成形・焼成している。この改良技術により、仮焼工程の省略は一応可能となったが、成形体の変形やひび割れの問題は完全には解決されていなかった。その理由は、Ｚｎフェライトは一旦形成されると安定であるが、Ｍｎフェライトは高温で形成されても冷却時に酸化されて一部再分解する為、Ｚｎを全く含まないＭｎ―Ｆｅ複合酸化鉄ではフェライト化が不十分な場合がある為と考えられる。
【０００６】
また、噴霧焙焼技術の改良により、塩化物蒸気圧の高いＺｎを揮散させずに複合酸化鉄粉体に取り込む方法も各種研究されており、燃焼後の還元性物質を含まない高温度の高速ガス流に原料液を噴霧し、熱ガス流と並流させて焙焼する方法（特開平１―１９２７０８号）や、それと類似の並流焙焼法（特開平３―４０９２１号）、或は噴霧焙焼時の噴霧液滴径や、焙焼中又は焙焼後の温度・時間・雰囲気等を規定したもの（特開平５―５１２１８号、特開平５―３３０８２８号、特開平６―２４４０１５号、特開平６―２９３５２１号）等、多数の改良技術が開示されている。
これらの改良技術により、確かにＺｎが複合酸化鉄中に取り込まれ、例えば特開平６―２９３５２１号に見られる様に、ミクロな組成偏差も殆ど無い均質なフェライト化した原料粉が得られ、それらを直接造粒・成形・焼成した場合、従来よりも特性の大幅に優れたコアが得られる事は判った。
しかし、これらの改良噴霧焙焼法の問題点は、Ｚｎを取り込む為にガス流れと液滴流れを並行とし、急速加熱・急速冷却を行なう為、従来の噴霧焙焼法に比べて熱原単位が大幅に悪化し、コストアップにつながる。折角、Ｆｅ、Ｍｎ、Ｚｎの複合酸化鉄を作り、仮焼工程を省略してもその原料粉が高価になってしまい、結局フェライト製品のコストダウンにはつながらないという問題点があった。
【０００７】
また、この金属塩の水溶液を噴霧焙焼して得られたフェライト原料粉を用いて、高透磁率フェライトを得ることも既に提案されている（特開平６―３４２７１６号）。しかし、Ｚｎ含有率の高いＭｎ―Ｚｎ系ソフトフェライトでは、金属塩の水溶液を噴霧焙焼してフェライト原料粉を得る場合、焙焼時のＺｎＯの蒸発に伴い、組成コントロールが非常に困難となる。
また、金属塩の水溶液を噴霧焙焼して得られたフェライト原料粉は、細かい粒子径の原料粉となり易く、この粒子径の細かい原料粉を用いてフェライト焼結体を製造する場合、低い温度で反応性を抑えながら焼結させることにより、比較的結晶粒径の小さいフェライト焼結体を得ることは出来るが、結晶粒径を大きくしようとして、焼結温度を上げると、たちまち急激な粒成長を生じ、結晶が粗大化して、透磁率が逆に低下してしまい、使用出来なくなる。
本発明は、複合酸化鉄粉を使用して、仮焼工程の省略を行うことができる安価なソフトフェライト原料粉を提供し、金属塩の水溶液を噴霧焙焼して得られた粒子径が細かいフェライト原料粉を用いて、結晶粒径をコントロールし、結晶粒径が大きく、かつ均一なＭｎ―Ｚｎ系ソフトフェライトを提供することを目的とする。
【０００８】
【課題を解決するための手段】
本発明は、Ｆｅ、Ｍｎ又はＦｅ、Ｍｎ、Ｚｎの各塩化物の水溶液を噴霧焙焼して、比表面積が４〜２５ｍ２／ｇで、且つＦｅ、Ｍｎ、Ｚｎの含有量がＦｅ２Ｏ３、ＭｎＯ、ＺｎＯのモル比に換算して、各４０〜６５％、１０〜５０％、０〜３５％の比率で含む複合酸化鉄粉を用意し、
この複合酸化鉄粉を全体の２０〜８０重量％とし、これに酸化鉄、酸化亜鉛、及び焼成してＭｎＯになるＭｎ化合物の粉末をそれぞれ所定のモル比で８０〜２０重量％混合したソフトフェライト原料粉に、更に焼結後にＬｉ、Ｂ、Ｍｇ、Ｓｉ、Ｋ、Ｃａ、Ｔｉ、Ｖ、Ｃｒ、Ｃｏ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｉｎ、Ｓｎ、Ｔｅ、Ｂａ、Ｈｆ、Ｔａ、Ｗ、ＴｌおよびＢｉの酸化物となる成分を１種乃至２種以上副成分として加え混合の後、このソフトフェライト原料粉を未仮焼のまま所定形状に成形して成形体となし、前記成形体を酸素濃度１％〜１０％で焼結し、焼結密度が理論密度の９５％以上で、かつ平均結晶粒径が１０〜５０μｍであり、全体のＦｅ、Ｍｎ、Ｚｎ含有量をＦｅ２Ｏ３、ＭｎＯ、ＺｎＯのモル比に換算して、各５０〜５５％、２０〜３５％、１５〜３０％のフェライト焼結体を得るフェライト焼結体の製造方法である。
【０００９】
【作用】
本発明では、複合酸化鉄粉と各酸化物などの生原料粉とを混ぜて使用することにより、仮焼なしで割れや変形のないソフトフェライトを得ることができる。即ち、Ｆｅ２Ｏ３、Ｍｎ３Ｏ４、ＺｎＯが混合された生原料粉中に、フェライト化が始まる５００〜６００℃の温度で焼結反応が起こり始めるような、比表面積の大きい活性度の高い複合酸化鉄粉が、重量比で２０％程度以上混合されていれば、フェライト化による体積膨張と焼結による体積収縮が打ち消し合い、焼結体の変形や割れは抑えられることが判った。混合比率の上限は、仮焼工程省略の観点からは特に制約が無いが、コストダウンの目的からは高価な複合酸化鉄粉を多く使用することは得策でなく、８０％以下が良い。また、複合酸化鉄粉の比表面積は、４〜２５ｍ２／ｇが適当となる。４ｍ２／ｇより小さいと焼結助剤としての効果が不十分であり、２５ｍ２／ｇより大きいとスラリー粘度が上がり過ぎ、使用し難い。好ましくは、６〜２０ｍ２／ｇである。また、複合酸化鉄は、スピネル化率が高い方が望ましく、好ましくは、９０％以上である。また、組成の均一性に関しては、仮焼していない生原料粉が混合されていても、低温で焼結反応が始まる活性度の高い複合酸化鉄粉が６０％以上混合されていれば１１００〜１２００℃程度、２０〜６０％の混合比率でも１２００〜１３００℃程度の焼成温度で十分拡散が起こり、実用上問題がないことが判った。この、焼成温度によって、焼結体の結晶粒径が変わり、従って、複合酸化鉄の混合比率、焼成温度の選択により、結晶粒径、電磁気特性を変更可能である。また、本発明では、複合酸化鉄粉に各酸化物などの生原料粉を混ぜて使用するため、複合酸化鉄粉の組成ずれが多少大きくても、後で混ぜる生原料により調整できるので、複合酸化鉄の噴霧焙焼時の精密制御が不要となり、設備費等のコストを低減できる。即ち、Ｆｅ、Ｍｎ、Ｚｎの組成比をミクロに見ても均一であるように厳密に制御しようとすると、揮散し易いＺｎを逃がさぬよう、例えば特開平６―２９３５２１号にあるように、噴霧焙焼時の液滴径、温度、雰囲気、冷却条件を厳しく制御しなければならず、急速加熱・急速冷却による熱ロスも大きくなるが、本発明によれば、焙焼時の組成ずれやミクロな組成の不均一はあまり問題にならず、製造方法の自由度が増し、コストダウンが可能となる。例えば、焙焼後のガスを冷却せずに、バグフィルターで製品を捕集した後、ダストの無いガスから十分に熱回収することもできる。また、本発明では、複合酸化鉄粉に各酸化物などの生原料粉を混ぜて使用するため、一つの複合酸化鉄粉から、組成の異なる複数種のフェライト製品の製造が可能である。もちろん、複合酸化鉄の混合量を２０〜８０重量％とし、目標とする組成も決定されれば、自ずと複合酸化鉄の組成範囲も制限される。これに対し、特開平６―２９３５２１号の様に複合酸化鉄粉を１００％使用する場合や、特公昭６３―１７７７６号の様に後から添加する粉の大部分はＺｎＯでＦｅ２Ｏ３、Ｍｎ３Ｏ４は微調整にしか用いない場合は、本発明の様にはできず、それぞれの複合酸化鉄粉を作り分けなければならない為、ロット切り替え時のロスが生じる。以上のことから、複合酸化鉄粉のＦｅ、Ｍｎ、Ｚｎの含有量は、Ｆｅ２Ｏ３、ＭｎＯ、ＺｎＯのモル比に換算して、各４０〜６５％、１０〜５０％、０〜３５％が適当である。もちろん、最終組成と同様の各５０〜５５％、２０〜３５％、１５〜３０％の範囲とする事は好ましく、また本発明は高透磁率材であるが、低損失材との共用を考えた場合、各々４５〜６０％、３０〜４５％、５〜１５％とすることもできる。また、全体のＦｅ、Ｍｎ、Ｚｎ含有量をＦｅ２Ｏ３、ＭｎＯ、ＺｎＯのモル比に換算して、各５０〜５５％、２０〜３５％、１５〜３０％としたのは、この範囲以外では、高透磁率特性を得ることが困難であるからである。複合酸化鉄粉と各酸化物などの生原料粉とを混ぜて使用することにより、焼結性のコントロールが可能となり、フェライト焼結体の焼結密度が理論密度の９５％以上で、かつ平均結晶粒径が１０〜５０μｍの範囲で制御できる。なお、本発明による技術が適用されるフェライトとしては、副成分として焼結後にＬｉ、Ｂ、Ｍｇ、Ｓｉ、Ｋ、Ｃａ、Ｔｉ、Ｖ、Ｃｒ、Ｃｏ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｉｎ、Ｓｎ、Ｔｅ、Ｂａ、Ｈｆ、Ｔａ、Ｗ、ＴｌおよびＢｉの酸化物となる成分を１種乃至２種以上含んでも良い。
【００１０】
【実施例】
以下に、本発明に係るフェライト材料の実施例を詳細に説明する。
実施例１
Ｆｅの塩化物とＭｎの塩化物とＺｎの塩化物とを混合した水溶液を噴霧焙焼して、Ｆｅ2Ｏ3、ＭｎＯ、ＺｎＯのモル比に換算して、Ｆｅ2Ｏ3 ５２．５ｍｏｌ％、ＭｎＯ ２５．５ｍｏｌ％、ＺｎＯ ２２．０ｍｏｌ％の成分を有する複合酸化鉄粉を用意し、この複合酸化鉄粉に対して、Ｆｅ2Ｏ3、Ｍｎ3Ｏ4、ＺｎＯの酸化物原料粉末（生原料粉）のそれぞれの粉末を上記と同組成となるように添加含有して、フェライト原料粉を作成した。このとき、複合酸化鉄粉の含有量を表１に示す種々の割合で作製した。尚、最終組成は、上記の組成となる様に設定した。このとき、Ｆｅ3Ｏ3の平均一次粒子径は、０．７８μｍ、Ｍｎ3Ｏ4の平均一次粒子径は、０．５６μｍ、ＺｎＯの平均一次粒子径は、０．６５μｍ、噴霧焙焼して得た複合酸化鉄粉の平均一次粒子径は、０．０８μｍ（比表面積が約１７ｍ2／ｇ）であった。これに、ＣａＣＯ3 １００ｐｐｍ、Ｂｉ2Ｏ3 ４００ｐｐｍ、さらに所定量のイオン交換水および分散剤を添加した後、アトライタにて１時間混合し、これに原料に対して２ｗｔ％のバインダー（ポリビニルアルコール）を加え、スプレードライヤにて造粒し、５０メッシュのふるいにて整粒した顆粒を乾式圧縮成形機と金型を用いて、外径１６．８ｍｍ、内径８．５ｍｍ、高さ５．４ｍｍのリング状コアに成形圧力２．５ｔｏｎ／ｃｍ2で成形した。これをバッチ式焼成炉を用いて、焼成温度１３４０℃、酸素分圧１０％で焼成し、得られた焼結体の焼結密度、初透磁率、平均結晶粒径を測定した。この結果を表１に示す。又、表１の備考欄に本発明の範囲のものは、本発明品とし、本発明の範囲外のものは比較例とした。
【００１１】
【表１】
この表１に示すとおり、噴霧焙焼して得た複合酸化鉄粉のみを使用した（Ｎｏ．６、１００％）場合、平均結晶粒径が１１３μｍと粗大化し、初透磁率が低下するが、本発明のように、酸化物粉末を混合することにより、平均結晶粒径が２０〜３４μｍとなり、高透磁率フェライト焼結体を得ることができた。また、本発明品の焼結密度は、理論密度（５１００ｋｇ／ｍ3）の９５％（４８５０ｋｇ／ｍ3）以上の密度を得ている。
【００１３】
実施例２
実施例１と同一手順で作製したリング状コアを、バッチ式焼成炉を用いて、焼成温度１２８０℃、酸素分圧１％で焼成し、得られた焼結体の焼結密度、初透磁率、平均結晶粒径を測定した。この結果を表２に示す。又、表２の備考欄に本発明の範囲のものは、本発明品とし、本発明の範囲外のものは比較例とした。
【００１４】
【表２】
この表２に示すとおり、本発明によれば、酸化物粉末を混合することにより、平均結晶粒径が１１〜１５μｍで、高透磁率のフェライト焼結体を得ることができた。また、本発明品の焼結密度は、理論密度（５１００ｋｇ／ｍ3）の９５％（４８５０ｋｇ／ｍ3）以上の密度を得ている。
【００１６】
実施例３
Ｆｅの塩化物とＭｎの塩化物とＺｎの塩化物を混合し、噴霧焙焼して得た複合酸化鉄粉であって、Ｆｅ、Ｍｎ、Ｚｎの含有量がＦｅ2Ｏ3、ＭｎＯ、ＺｎＯのモル比に換算して、Ｆｅ2Ｏ3 ５２．５ｍｏｌ％、ＭｎＯ ２５．５ｍｏｌ％、ＺｎＯ ２２．０ｍｏｌ％の複合酸化鉄粉と、Ｆｅ2Ｏ3、Ｍｎ3Ｏ4、ＺｎＯの相当量のそれぞれの酸化物原料粉末とを表３に示す最終組成になるように、種々の割合で配合した。このとき、複合酸化鉄粉の含有量が６０ｗｔ％となるように設定した。そして、Ｆｅ2Ｏ3の平均一次粒子径は、０．７８μｍ、Ｍｎ3Ｏ4の平均一次粒子径は、０．５６μｍ、ＺｎＯの平均一次粒子径は、０．６５μｍ、噴霧焙焼して得たフェライト原料粉の平均一次粒子径は、０．０８μｍであった。これに、表３に示す所定量の添加物を副成分として加え、さらに所定量のイオン交換水および分散剤を添加した後、アトライタにて１時間混合し、これに原料に対して２ｗｔ％のバインダー（ポリビニルアルコール）を加え、スプレードライヤにて造粒し、５０メッシュのふるいにて整粒した顆粒を乾式圧縮成形機と金型を用いて、外径１６．８ｍｍ、内径８．５ｍｍ、高さ５．４ｍｍのリング状コアに成形圧力２．５ｔｏｎ／ｃｍ2で成形した。これをバッチ式焼成炉を用いて、表４の焼成条件で焼成し、得られた焼結体の焼結密度、初透磁率、平均結晶粒径を測定した。この結果を表４に示す。
【００１７】
【表３】
【表４】
上記表３、表４において、試料Ｎｏ．１３は比較例であり、試料Ｎｏ．１４，１５は実施例である。本発明の実施例では、噴霧焙焼して得た複合酸化鉄粉の含有量を６０ｗｔ％とし、これに生原料粉を添加して、種々の所望の組成のソフトフェライトを得ることができた。しかも、高透磁率であり、焼結密度が理論密度の９５％以上であって、平均結晶粒径が１０〜５０μｍの範囲である。
【００２０】
実施例４
Ｆｅの塩化物とＭｎの塩化物とＺｎの塩化物とを混合した水溶液を噴霧焙焼して、Ｆｅ2Ｏ3、ＭｎＯ、ＺｎＯのモル比に換算して、Ｆｅ2Ｏ3 ５２．５ｍｏｌ％、ＭｎＯ ２５．５ｍｏｌ％、ＺｎＯ ２２．０ｍｏｌ％の成分を有する複合酸化鉄粉を用意し、この複合酸化鉄粉に対して、Ｆｅ2Ｏ3、Ｍｎ3Ｏ4、ＺｎＯの酸化物原料粉末（生原料粉）のそれぞれの粉末を上記と同組成となるように添加含有して、フェライト原料粉を作成した。このとき、複合酸化鉄粉の含有量が６０ｗｔ％となるように作製した。尚、最終組成は、上記の組成となる様に設定した。このとき、Ｆｅ2Ｏ3の平均一次粒子径は、０．７８μｍ、Ｍｎ3Ｏ4の平均一次粒子径は、０．５６μｍ、ＺｎＯの平均一次粒子径は、０．６５μｍ、噴霧焙焼して得た複合酸化鉄粉の平均一次粒子径は、０．０８μｍ（比表面積が約１７ｍ2／ｇ）であった。これに、ＣａＣＯ3 １００ｐｐｍ、Ｂｉ2Ｏ3 ４００ｐｐｍ、さらに所定量のイオン交換水および分散剤を添加した後、アトライタにて１時間混合し、これに原料に対して２ｗｔ％のバインダー（ポリビニルアルコール）を加え、スプレードライヤにて造粒し、５０メッシュのふるいにて整粒した顆粒を乾式圧縮成形機と金型を用いて、外径１６．８ｍｍ、内径８．５ｍｍ、高さ５．４ｍｍのリング状コアに成形圧力２．５ｔｏｎ／ｃｍ2で成形した。これをバッチ式焼成炉を用いて、表５に示す焼成温度、酸素分圧で焼成し、得られた焼結体の焼結密度、初透磁率、平均結晶粒径を測定した。この結果を表５に示す。
【００２１】
【表５】
この表５に示すように、本発明では、焼成条件により結晶粒径のコントロールが可能であり、それにより所望の高透磁率を得ることができる。
また、この表５において、試料Ｎｏ．１９は、焼成時に成形体を同組成のフェライトケースで囲って焼成させたものである。
【００２３】
以上、実施例に示すように、本発明の実施例は、噴霧焙焼して得た複合酸化鉄粉の含有量としては、２０〜８０ｗｔ％とし、これに生原料粉を所定量添加して、所望の組成のソフトフェライトを得ることができた。しかも、本発明の実施例は、高透磁率フェライトとして使用可能なものであり、焼結密度が理論密度の９５％以上であって、平均結晶粒径が１０〜５０μｍの範囲で制御することが出来ている。
【００２４】
【発明の効果】
本発明によれば、複合酸化鉄粉と生原料粉とを所定量混合して使用することにより、仮焼工程を省略して、ソフトフェライトの製造が可能となるものであり、高透磁率Ｍｎ―Ｚｎ系ソフトフェライトを安価に製造することが可能となる。また、本発明によれば、フェライト焼結体の結晶粒径のコントロールも可能となる。[0001]
[Industrial application fields]
The present invention relates to a soft ferrite raw material powder for inexpensively producing Mn—Zn soft ferrite having characteristics equivalent to or better than those of products according to the prior art, and in particular, an Mn—Zn soft ferrite raw material powder having high magnetic permeability characteristics. The present invention relates to a ferrite sintered body and a method for producing the same.
[0002]
[Prior art]
Conventional Mn—Zn-based soft ferrites are prepared by weighing and mixing Fe 2 O 3 , Mn 3 O 4 , and ZnO oxides in predetermined amounts, and calcining the mixture at 800 to 1000 ° C. Pulverizing the calcined body, adding desired additives and binder, granulating it, filling it into a mold, forming it into a predetermined shape, firing at a high temperature of 1300-1400 ° C, An Mn—Zn-based soft ferrite core is obtained through necessary processing such as a polishing process.
As described above, the conventional method for obtaining Mn—Zn-based soft ferrite has a long process and is complicated, and there is a problem that the cost is increased because it undergoes calcination and main firing and two firing steps.
The reason for this calcining is to homogenize the components and promote the ferritization reaction (Hiraga, Okutani, Ojima, Ferrite, Maruzen, Sho 61.11.30, p48-51). When raw raw powder that is not directly granulated, shaped, and fired, there arises a problem that deformation and cracking occur due to volume expansion by a ferritization reaction at 500 to 900 ° C. and subsequent volume shrinkage by a sintering reaction.
[0003]
On the other hand, several methods for obtaining composite iron oxide powder containing Fe, Mn, and the like have been proposed as improved techniques aimed at omitting the calcination step and improving quality.
For example, as described in Japanese Examined Patent Publication Nos. 47-11550 and 63-177776, a ferrite-constituting metal chloride is mixed in an aqueous solution, then sprayed and roasted in a high-temperature gas, and directly equivalent to a calcined powder. There is a way to get a body. In addition to cost reduction due to omission of the calcination step, this method is expected to have a merit of superior homogenization of components and improved quality because of mixing in a molten state.
[0004]
One of the main uses of this Mn—Zn soft ferrite raw material powder is a transformer and a noise filter for communication equipment. The Mn—Zn soft ferrite used in such communication devices is desired to have a high magnetic permeability in order to reduce the weight, thickness and size of the product. In order to obtain this high magnetic permeability, the crystal grain size should be large and uniform. In the firing step, firing is performed at a high temperature for a long time.
[0005]
[Problems to be solved by the invention]
In the conventional method of obtaining composite iron oxide powder, as described in Japanese Patent Publication No. 63-17776, Zn having a high vapor pressure of chloride is volatilized first, and the composite iron oxide powder after roasting is obtained. There is a problem that it is difficult to be taken in.
In order to solve this problem, Japanese Patent Publication No. 63-17776 uses only the feature that ZnO easily causes a ferritization reaction, so that only an aqueous chloride solution of Fe and Mn having a low chloride vapor pressure is mixed and sprayed. After baking, the obtained powder is mixed with ZnO powder and granulated, molded and fired. With this improved technique, the calcination step can be omitted, but the problems of deformation and cracking of the molded body have not been completely solved. The reason is that once the Zn ferrite is formed, it is stable, but even if the Mn ferrite is formed at a high temperature, it is oxidized during cooling and partially re-decomposed. This is thought to be due to the fact that ferritization may be insufficient.
[0006]
In addition, various methods have been studied for improving the spray roasting technology to incorporate Zn with high chloride vapor pressure into the composite iron oxide powder without volatilization. A method of spraying a raw material liquid into a gas flow and co-firing with a hot gas flow (Japanese Patent Laid-Open No. 1-192708), a similar co-current roasting method (Japanese Patent Laid-Open No. 3-40921), or Specified spray droplet diameter at spray roasting, temperature, time, atmosphere, etc. during or after roasting (JP-A-5-51218, JP-A-5-330828, JP-A-6-244015) JP-A-6-293521) and many other improved techniques are disclosed.
With these improved techniques, Zn is certainly incorporated into the composite iron oxide, and as shown in, for example, JP-A-6-293521, homogeneous ferritized raw material powders having almost no micro compositional deviation can be obtained. It was found that a core with significantly improved characteristics can be obtained by directly granulating, molding, and firing.
However, the problem with these improved spray roasting methods is that the gas flow and droplet flow are parallel in order to incorporate Zn, and rapid heating and cooling are performed. Will greatly deteriorate, leading to increased costs. Even if a complex iron oxide of Fe, Mn, and Zn is made and the calcining step is omitted, the raw material powder becomes expensive, and there is a problem that it does not lead to cost reduction of the ferrite product.
[0007]
In addition, it has already been proposed to obtain high permeability ferrite by using ferrite raw material powder obtained by spray roasting of an aqueous solution of this metal salt (Japanese Patent Laid-Open No. 6-342716). However, in the case of Mn—Zn soft ferrite having a high Zn content, when ferrite raw material powder is obtained by spray roasting an aqueous solution of a metal salt, composition control becomes very difficult as ZnO evaporates during roasting. .
Moreover, the ferrite raw material powder obtained by spray roasting an aqueous solution of a metal salt is likely to be a raw material powder having a fine particle size, and when a ferrite sintered body is produced using the raw material powder having a fine particle size, the temperature is low. By sintering while suppressing the reactivity, a ferrite sintered body with a relatively small crystal grain size can be obtained. However, if the sintering temperature is raised to increase the crystal grain size, rapid grain growth is achieved. And the crystal becomes coarse, and the magnetic permeability is decreased, making it unusable.
The present invention provides an inexpensive soft ferrite raw material powder capable of omitting the calcination step using composite iron oxide powder, and has a fine particle size obtained by spray roasting an aqueous solution of a metal salt. An object of the present invention is to provide a uniform Mn—Zn-based soft ferrite having a large crystal grain size and a uniform crystal grain size by using ferrite raw material powder.
[0008]
[Means for Solving the Problems]
In the present invention, an aqueous solution of each chloride of Fe, Mn or Fe, Mn, and Zn is spray roasted to have a specific surface area of 4 to 25 m 2 / g and a content of Fe, Mn, and Zn of Fe 2 O. 3 , Prepared composite iron oxide powder containing 40 to 65%, 10 to 50%, and 0 to 35% ratio in terms of molar ratio of MnO and ZnO,
Soft ferrite in which this composite iron oxide powder is mixed in an amount of 20 to 80% by weight and mixed with iron oxide, zinc oxide, and powder of Mn compound that is fired to become MnO at a predetermined molar ratio of 80 to 20% by weight. After sintering further to Li, B, Mg, Si, K, Ca, Ti, V, Cr, Co, Y, Zr, Nb, Mo, In, Sn, Te, Ba, Hf, Ta, W, After adding and mixing one or more components that become oxides of Tl and Bi as subcomponents, this soft ferrite raw material powder is formed into a predetermined shape without being pre- calcined to form a molded body. Sintering is performed at an oxygen concentration of 1% to 10%, the sintered density is 95% or more of the theoretical density, the average crystal grain size is 10 to 50 μm, and the total Fe, Mn, Zn content is Fe 2 O 3. , 50 to 55 in terms of molar ratio of MnO and ZnO , From 20 to 35% the manufacturing method of the ferrite sintered body to obtain a 15% to 30% of the ferrite sintered body.
[0009]
[Action]
In the present invention, soft ferrite free from cracking and deformation can be obtained without calcining by mixing and using composite iron oxide powder and raw material powder such as each oxide. That is, in the raw material powder in which Fe 2 O 3 , Mn 3 O 4 and ZnO are mixed, an activity with a large specific surface area such that a sintering reaction starts to occur at a temperature of 500 to 600 ° C. where ferritization starts. It has been found that if high composite iron oxide powder is mixed in a weight ratio of about 20% or more, volume expansion due to ferritization and volume shrinkage due to sintering cancel each other, and deformation and cracking of the sintered body can be suppressed. The upper limit of the mixing ratio is not particularly limited from the viewpoint of omitting the calcining step, but for the purpose of cost reduction, it is not a good idea to use a large amount of expensive composite iron oxide powder, and 80% or less is good. The specific surface area of the composite iron oxide powder is suitably 4 to 25 m 2 / g. If it is smaller than 4 m 2 / g, the effect as a sintering aid is insufficient, and if it is larger than 25 m 2 / g, the slurry viscosity is excessively increased and is difficult to use. Preferably, it is 6-20 m < 2 > / g. The composite iron oxide preferably has a higher spinelization rate, and is preferably 90% or more. In addition, regarding the uniformity of composition, even if raw raw powder that has not been calcined is mixed, if composite iron oxide powder having a high activity at which the sintering reaction starts at a low temperature is mixed by 60% or more, 1100 It was found that even at a mixing ratio of about 1200 ° C. and 20 to 60%, sufficient diffusion occurred at a firing temperature of about 1200 to 1300 ° C. and there was no practical problem. The crystal grain size of the sintered body varies depending on the firing temperature. Therefore, the crystal grain size and electromagnetic characteristics can be changed by selecting the mixing ratio of the composite iron oxide and the firing temperature. In the present invention, since raw material powder such as each oxide is mixed with the composite iron oxide powder, even if the composition deviation of the composite iron oxide powder is somewhat large, it can be adjusted by the raw material to be mixed later. Precise control at the time of iron oxide spray roasting is not necessary, and costs such as equipment costs can be reduced. That is, if the composition ratio of Fe, Mn, and Zn is strictly controlled so as to be uniform even when viewed microscopically, Zn that is easily volatilized is not escaped. For example, as disclosed in JP-A-6-293521, The droplet diameter, temperature, atmosphere, and cooling conditions during roasting must be strictly controlled, and heat loss due to rapid heating / cooling increases. Such a non-uniform composition is not a significant problem, increasing the degree of freedom of the manufacturing method and reducing the cost. For example, after collecting the product with a bag filter without cooling the gas after roasting, it is possible to sufficiently recover heat from the dust-free gas. Moreover, in this invention, since raw raw material powders, such as each oxide, are mixed and used for composite iron oxide powder, the manufacture of the multiple types of ferrite product from which a composition differs from one composite iron oxide powder is possible. Of course, if the mixing amount of the composite iron oxide is 20 to 80% by weight and the target composition is determined, the composition range of the composite iron oxide is naturally limited. On the other hand, when 100% of the composite iron oxide powder is used as in JP-A-6-293521, or most of powder added later as in JP-B 63-17776 is ZnO, Fe 2 O 3 , When Mn 3 O 4 is used only for fine adjustment, it cannot be performed as in the present invention, and each composite iron oxide powder must be prepared separately, resulting in loss during lot switching. From the above, the Fe, Mn, and Zn contents of the composite iron oxide powder are each 40 to 65%, 10 to 50%, and 0 to 35 in terms of the molar ratio of Fe 2 O 3 , MnO, and ZnO. % Is appropriate. Of course, it is preferable to make each of the ranges from 50 to 55%, 20 to 35%, and 15 to 30% similar to the final composition, and the present invention is a high permeability material, but it is considered to be shared with a low loss material. In this case, it may be 45 to 60%, 30 to 45%, and 5 to 15%, respectively. In addition, it is this range that the total Fe, Mn, and Zn contents are converted to molar ratios of Fe 2 O 3 , MnO, and ZnO to be 50 to 55%, 20 to 35%, and 15 to 30%, respectively. This is because it is difficult to obtain high magnetic permeability characteristics except for the above. By mixing and using composite iron oxide powder and raw material powder such as each oxide, it becomes possible to control the sinterability, the sintered density of the ferrite sintered body is 95% or more of the theoretical density, and the average The crystal grain size can be controlled in the range of 10 to 50 μm. The ferrite to which the technology according to the present invention is applied includes Li, B, Mg, Si, K, Ca, Ti, V, Cr, Co, Y, Zr, Nb, Mo, In, and the like after sintering as subcomponents. One or two or more types of components that form oxides of Sn, Te, Ba, Hf, Ta, W, Tl, and Bi may be included.
[0010]
【Example】
Below, the example of the ferrite material concerning the present invention is described in detail.
Example 1
An aqueous solution in which Fe chloride, Mn chloride and Zn chloride are mixed is spray-roasted and converted to a molar ratio of Fe 2 O 3 , MnO and ZnO, and Fe 2 O 3 is 52.5 mol%. , MnO 25.5 mol% and ZnO 22.0 mol% of the composite iron oxide powder is prepared, Fe 2 O 3 , Mn 3 O 4 , ZnO oxide raw material powder ( Each raw material powder) was added and contained so as to have the same composition as described above to prepare a ferrite raw material powder. At this time, the content of the composite iron oxide powder was prepared at various ratios shown in Table 1. The final composition was set to be the above composition. At this time, the average primary particle diameter of Fe 3 O 3 is 0.78 μm, the average primary particle diameter of Mn 3 O 4 is 0.56 μm, the average primary particle diameter of ZnO is 0.65 μm, and spray roasting is performed. The average primary particle diameter of the obtained composite iron oxide powder was 0.08 μm (specific surface area was about 17 m 2 / g). To this, 100 ppm of CaCO 3 , 400 ppm of Bi 2 O 3 , a predetermined amount of ion exchange water and a dispersing agent were added, and then mixed for 1 hour in an attritor, and 2 wt% binder (polyvinyl alcohol) with respect to the raw material. , Granulated with a spray dryer, and granulated with a 50 mesh sieve, using a dry compression molding machine and a mold, the outer diameter is 16.8 mm, the inner diameter is 8.5 mm, and the height is 5.4 mm. The ring-shaped core was molded at a molding pressure of 2.5 ton / cm 2 . This was fired at a firing temperature of 1340 ° C. and an oxygen partial pressure of 10% using a batch-type firing furnace, and the sintered density, initial permeability, and average crystal grain size of the obtained sintered body were measured. The results are shown in Table 1. Also, in the remarks column of Table 1, those within the scope of the present invention are those of the present invention, and those outside the scope of the present invention are comparative examples.
[0011]
[Table 1]
As shown in Table 1, when only the composite iron oxide powder obtained by spray roasting was used (No. 6, 100%), the average crystal grain size was coarsened to 113 μm, and the initial permeability decreased. As in the present invention, by mixing the oxide powder, the average crystal grain size became 20 to 34 μm, and a high permeability ferrite sintered body could be obtained. Further, the sintered density of the product of the present invention is 95% (4850 kg / m 3 ) or more of the theoretical density (5100 kg / m 3 ).
[0013]
Example 2
The ring-shaped core produced in the same procedure as in Example 1 was fired at a firing temperature of 1280 ° C. and an oxygen partial pressure of 1% using a batch-type firing furnace, and the sintered density and initial permeability of the obtained sintered body. The average crystal grain size was measured. The results are shown in Table 2. Further, in the remarks column of Table 2, those within the scope of the present invention are those of the present invention, and those outside the scope of the present invention are comparative examples.
[0014]
[Table 2]
As shown in Table 2, according to the present invention, a ferrite sintered body having an average crystal grain size of 11 to 15 μm and a high magnetic permeability could be obtained by mixing oxide powder. Further, the sintered density of the product of the present invention is 95% (4850 kg / m 3 ) or more of the theoretical density (5100 kg / m 3 ).
[0016]
Example 3
A composite iron oxide powder obtained by mixing Fe chloride, Mn chloride, and Zn chloride and spray roasting, wherein the content of Fe, Mn, Zn is Fe 2 O 3 , MnO, ZnO In terms of the molar ratio of Fe 2 O 3 52.5 mol%, MnO 25.5 mol%, ZnO 22.0 mol% of complex iron oxide powder, and Fe 2 O 3 , Mn 3 O 4 , ZnO Each oxide raw material powder was blended in various proportions so as to have the final composition shown in Table 3. At this time, it set so that content of complex iron oxide powder might be 60 wt%. The average primary particle diameter of Fe 2 O 3 is 0.78 μm, the average primary particle diameter of Mn 3 O 4 is 0.56 μm, the average primary particle diameter of ZnO is 0.65 μm, and obtained by spray roasting. The average primary particle diameter of the ferrite raw material powder was 0.08 μm. To this, a predetermined amount of additives shown in Table 3 were added as subcomponents, a predetermined amount of ion-exchanged water and a dispersant were added, and then mixed for 1 hour in an attritor. Add a binder (polyvinyl alcohol), granulate with a spray dryer, and adjust the size of the granules with a 50-mesh sieve using a dry compression molding machine and a mold, outer diameter 16.8 mm, inner diameter 8.5 mm, high A 5.4 mm ring-shaped core was molded at a molding pressure of 2.5 ton / cm 2 . This was fired under the firing conditions shown in Table 4 using a batch-type firing furnace, and the sintered density, initial permeability, and average crystal grain size of the obtained sintered body were measured. The results are shown in Table 4.
[0017]
[Table 3]
[Table 4]
In Tables 3 and 4 above , Sample No. 13 is a comparative example. Reference numerals 14 and 15 are examples. In the examples of the present invention, the content of the composite iron oxide powder obtained by spray roasting is 60 wt%, and raw raw material powder can be added thereto to obtain soft ferrites having various desired compositions. It was. In addition, the magnetic permeability is high, the sintered density is 95% or more of the theoretical density, and the average crystal grain size is in the range of 10 to 50 μm.
[0020]
Example 4
An aqueous solution in which Fe chloride, Mn chloride and Zn chloride are mixed is spray-roasted and converted to a molar ratio of Fe 2 O 3 , MnO and ZnO, and Fe 2 O 3 is 52.5 mol%. , MnO 25.5 mol% and ZnO 22.0 mol% of the composite iron oxide powder is prepared, Fe 2 O 3 , Mn 3 O 4 , ZnO oxide raw material powder ( Each raw material powder) was added and contained so as to have the same composition as described above to prepare a ferrite raw material powder. At this time, it produced so that content of composite iron oxide powder might be 60 wt%. The final composition was set to be the above composition. At this time, the average primary particle diameter of Fe 2 O 3 is 0.78 μm, the average primary particle diameter of Mn 3 O 4 is 0.56 μm, the average primary particle diameter of ZnO is 0.65 μm, and spray roasting is performed. The average primary particle diameter of the obtained composite iron oxide powder was 0.08 μm (specific surface area was about 17 m 2 / g). To this, 100 ppm of CaCO 3 , 400 ppm of Bi 2 O 3 , a predetermined amount of ion exchange water and a dispersing agent were added, and then mixed for 1 hour in an attritor, and 2 wt% binder (polyvinyl alcohol) with respect to the raw material. , Granulated with a spray dryer, and granulated with a 50 mesh sieve, using a dry compression molding machine and a mold, the outer diameter is 16.8 mm, the inner diameter is 8.5 mm, and the height is 5.4 mm. The ring-shaped core was molded at a molding pressure of 2.5 ton / cm 2 . This was fired at a firing temperature and an oxygen partial pressure shown in Table 5 using a batch-type firing furnace, and the sintered density, initial permeability, and average crystal grain size of the obtained sintered body were measured. The results are shown in Table 5.
[0021]
[Table 5]
As shown in Table 5, in the present invention, the crystal grain size can be controlled by the firing conditions, whereby a desired high magnetic permeability can be obtained.
In Table 5, Sample No. No. 19 is a product which is fired by being surrounded by a ferrite case of the same composition during firing.
[0023]
As mentioned above, as shown in the Examples, the content of the composite iron oxide powder obtained by spray roasting is 20 to 80 wt%, and a predetermined amount of raw material powder is added thereto. Thus, soft ferrite having a desired composition could be obtained. Moreover, the examples of the present invention can be used as high permeability ferrite, and the sintered density is 95% or more of the theoretical density, and the average crystal grain size can be controlled in the range of 10 to 50 μm. It is done.
[0024]
【The invention's effect】
According to the present invention, by mixing and using a predetermined amount of composite iron oxide powder and raw material powder, it is possible to produce a soft ferrite by omitting the calcination step, and high permeability Mn -Zn-based soft ferrite can be manufactured at low cost. Further, according to the present invention, the crystal grain size of the ferrite sintered body can be controlled.
Claims (1)
この複合酸化鉄粉を全体の２０〜８０重量％とし、これに酸化鉄、酸化亜鉛、及び焼成してＭｎＯになるＭｎ化合物の粉末をそれぞれ所定のモル比で８０〜２０重量％混合したソフトフェライト原料粉に、更に焼結後にＬｉ、Ｂ、Ｍｇ、Ｓｉ、Ｋ、Ｃａ、Ｔｉ、Ｖ、Ｃｒ、Ｃｏ、Ｙ、Ｚｒ、Ｎｂ、Ｍｏ、Ｉｎ、Ｓｎ、Ｔｅ、Ｂａ、Ｈｆ、Ｔａ、Ｗ、ＴｌおよびＢｉの酸化物となる成分を１種乃至２種以上副成分として加え混合の後、このソフトフェライト原料粉を未仮焼のまま所定形状に成形して成形体となし、前記成形体を酸素濃度１％〜１０％で焼結し、焼結密度が理論密度の９５％以上で、かつ平均結晶粒径が１０〜５０μｍであり、全体のＦｅ、Ｍｎ、Ｚｎ含有量をＦｅ２Ｏ３、ＭｎＯ、ＺｎＯのモル比に換算して、各５０〜５５％、２０〜３５％、１５〜３０％のフェライト焼結体を得ることを特徴とするフェライト焼結体の製造方法。An aqueous solution of Fe, Mn or Fe, Mn, and Zn chlorides is spray roasted to have a specific surface area of 4 to 25 m 2 / g and Fe, Mn, and Zn contents of Fe 2 O 3 , MnO, In terms of the molar ratio of ZnO, a composite iron oxide powder containing 40 to 65%, 10 to 50%, and 0 to 35% ratio is prepared.
Soft ferrite in which this composite iron oxide powder is mixed in an amount of 20 to 80% by weight and mixed with iron oxide, zinc oxide, and powder of Mn compound that is fired to become MnO at a predetermined molar ratio of 80 to 20% by weight. After sintering further to Li, B, Mg, Si, K, Ca, Ti, V, Cr, Co, Y, Zr, Nb, Mo, In, Sn, Te, Ba, Hf, Ta, W, After adding and mixing one or more components that become oxides of Tl and Bi as subcomponents, this soft ferrite raw material powder is formed into a predetermined shape without being pre- calcined to form a molded body. Sintering is performed at an oxygen concentration of 1% to 10%, the sintered density is 95% or more of the theoretical density, the average crystal grain size is 10 to 50 μm, and the total Fe, Mn, Zn content is Fe 2 O 3. , 50 to 55 in terms of molar ratio of MnO and ZnO 20 to 35% the manufacturing method of the ferrite sintered body, characterized in that to obtain a 15% to 30% of the ferrite sintered body.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14888795A JP3852623B2 (en) | 1995-06-15 | 1995-06-15 | Method for producing ferrite sintered body |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14888795A JP3852623B2 (en) | 1995-06-15 | 1995-06-15 | Method for producing ferrite sintered body |
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| Publication Number | Publication Date |
|---|---|
| JPH08337466A JPH08337466A (en) | 1996-12-24 |
| JP3852623B2 true JP3852623B2 (en) | 2006-12-06 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP14888795A Expired - Fee Related JP3852623B2 (en) | 1995-06-15 | 1995-06-15 | Method for producing ferrite sintered body |
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| JP6649799B2 (en) * | 2016-02-25 | 2020-02-19 | 株式会社トーキン | Ferrite core and method of manufacturing ferrite core |
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